datapath: handle NF_REPEAT from nf_conntrack_in()

datapath: handle NF_REPEAT from nf_conntrack_in()

Upstream commit:
    commit 08733a0cb7decce40bbbd0331a0449465f13c444
    Author: Pablo Neira Ayuso <pablo@netfilter.org>
    Date:   Thu Nov 3 10:56:43 2016 +0100

    netfilter: handle NF_REPEAT from nf_conntrack_in()

    NF_REPEAT is only needed from nf_conntrack_in() under a very specific
    case required by the TCP protocol tracker, we can handle this case
    without returning to the core hook path. Handling of NF_REPEAT from the
    nf_reinject() is left untouched.

    Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
[Committer notes]
    Shift the functionality into the compat code, protected by v4.10
    version check. This allows the datapath/conntrack.c to match
    upstream.

Signed-off-by: Jarno Rajahalme <jarno@ovn.org>
Signed-off-by: Joe Stringer <joe@ovn.org>